1. Field of the Invention
The invention relates to a method for monitoring an electrical drive, in particular a drive of an armature, wherein electric power supply lines of the drive, which extend through a switchgear plug-in unit associated with the drive, are connected to a measurement and evaluation unit.
The invention also relates to an apparatus for monitoring an electrical drive, in particular a drive of an armature, wherein electrical power supply lines of the drive extend through a switchgear plug-in unit associated with the drive and wherein pickups for a measurement and evaluation unit are disposed at the plug-in unit.
The functional status of an armature is monitored by monitoring an electrical drive of the armature. In that way, trouble or changes in the operating performance of the armature can be recognized early. Such troubles do not yet impair the reliability of the armature but can cause later safety-relevant damage to the armature. The early recognition of the trouble makes it possible to repair or replace the armature in time. Consequently, safety-relevant damage does not occur, and such damage must especially be avoided in plants or systems with stringent requirements for safety or availability. Such plants or systems may be nuclear power plants, manufacturing plants, or chemical plants.
Electric power lines of a drive are typically extended through a plug-in unit of switchgear. Such a plug-in unit is known from Brockhaus Naturwissenschaften und Technik [Brockhaus Natural Sciences and Technology], Vol. 1, 1983, page 302. One such plug-in unit is available for each drive. Located in such a plug-in unit are a control unit and other electronic components. A voltage power unit and contactors for the drive are also disposed in it.
A testing method and a testing unit for an electrical drive is known from German Patent DE 29 17 529 C2.
In a method for monitoring a drive which is known from Published European Application No. 0 301 358 A1, corresponding to U.S. Pat. No. 4,829,234, a resistor is incorporated into the current circuit of the drive in order to measure the current intensity. That impairs operation of the drive during the measurement process.
It is known from Published European Application No. 0 355 255 A2 to mount a component on a unit for measurement purposes. The component, which includes electrical and electronic parts, impairs the operation of the unit during the measurement.
With the known methods and apparatuses, either the availability of the drive and in particular of an armature is restricted by the tests which are required, or else intervention must be made into the operation of the system or the plant containing the drive, in order to test the drive. In order to keep the disruption in operation slight, testing can therefore be done only at intervals over time. From that it can be concluded that individual problems or trouble occurring between tests cannot be detected.
In the event that a plug-in unit which, for instance, is known from Brockhaus Naturwissenschaften und Technik, is associated with the drive to be monitored, it is conventional, in order to carry out monitoring of a drive, to remove the corresponding plug-in unit from the switchgear and replace it with a plug-in measurement unit.
The drive is accordingly relieved of its own task. An armature moved by the drive is stopped, so that the drive can be tested within a limited measurement test run.
It may be necessary, after removal of the plug-in unit, to insert a plug-in adapter unit with which measuring instruments can be connected.
A known plug-in measurement unit or plug-in adapter unit contains different cabling from a plug-in unit intended for long-term operation. Line bindings for the voltage measurement are located in the measuring plug-in unit, on the electric power lines of the drive. Those lines are connected to voltage pickups, which are constructed as plug contacts, on the plug-in measurement unit. In order to measure current intensity, the power lines in the plug-in measurement unit are interrupted. The two ends of a line are connected to a voltage pickup in the form of plug contacts on the measurement plug-in unit.
The plug-in measurement unit differs from the plug-in unit for normal operation of the drive in particular in that the power lines are interrupted for the current intensity measurement.
As a rule, the measurement and evaluation unit is connected to the voltage and current pickups of the plug-in measurement unit. In it, the effective power is determined from the voltage and from the current intensity and is a measure of the status of an armature.
The known method and the apparatus suitable for performing it are complicated and difficult to handle. In the case of each monitoring operation, not only must the drive to be monitored be out of operation, which affects the operation of the entire system or plant, but moreover the plug-in unit associated with the drive in the switchgear must be replaced with a plug-in measurement unit or a plug-in adapter unit. The frequent replacement of plug-in units in the switchgear can cause damage to the plug-in units or the switchgear. Continued operation of a drive and therefore of an armature during the test process is not possible, since the power lines are interrupted when the plug-in units are changed.